(CNN) — Sen. John McCain, prominent among the Washington ranks who have questioned former Sen. Chuck Hagel’s suitability for the top Defense Department post, said Sunday he will not exert his power to block Hagel’s nomination.

“No,” he told CNN when asked directly whether he would block the nomination in the Senate. “I plan to make a judgment as to whether I think he’s appropriate to be Secretary of Defense or not.”

Each senator has the power to prevent a nomination from advancing to the floor, and one of McCain’s close colleagues, Sen. Lindsey Graham, has suggested he would put President Barack Obama’s nominee to lead the CIA on hold while awaiting answers on the U.S. Consulate attack in September in Benghazi, Libya.

McCain said he does not plan to block that nomination or that of John Brennan for the CIA, either. He said he does have questions for both.

Of Hagel, the Arizona Republican said, “There will be a number of questions about his view of America’s role in the world, about Iraq, about Afghanistan, about Iran, the threat of Iran.”

McCain also described his reservations regarding Hagel’s remark “that (the) surge in Iraq would be the greatest blunder since the Vietnam War, which is clearly a bizarre statement.”

Some senators from both sides of the aisle have expressed their concern about selecting the former Nebraska Republican to lead the Pentagon. McCain’s reservations stand out in part because of their once-vibrant friendship and partnership. Both were injured in the Vietnam War.

Some have described their difference in Iraq war policy as a stress point in the relationship. After McCain aided Hagel in his first campaign for the U.S. Senate, Hagel returned the favour as a national co-chair of his 2000 presidential bid. Hagel stayed out of the race when McCain ran again in 2008.

McCain told CNN last week that he hoped their friendship remained.

“The friendship, I hope, is still there,” he said on “The Situation Room,” saying their world views had split “rather dramatically.”

“I respect, admire, and call him a friend, but I have very serious questions about whether he will serve in the way that I think serves America’s best national interests.”

Officials supportive of Hagel’s confirmation but spoke to the media on the condition of anonymity have gone on the offensive in support of the nominee.

In response to charges he has not been a staunch supporter of Israel and expresses sympathies toward Iran, the officials pointed to votes he cast in favor of military aid to Israel and his recent call for the U.S. to “keep racheting up sanctions” on Iran, among other evidence. They also highlighted his leadership experience as evidence he is ready to direct the massive government department.

Critics have also taken issue with Hagel’s 1998 description of an ambassadorial nominee as “openly, aggressively gay” — for which he has since apologized — and his remark in 2007 when he said the “Jewish lobby intimidated lawmakers.”

McCain said Sunday on CBS’ “Face the Nation” that if asked today, he would not vote against Hagel, “nor would I vote for him.”

In his statement after Obama announced Hagel as his pick, McCain said, “Chuck Hagel served our nation with honor in Vietnam, and I congratulate him on this nomination.

“I have serious concerns about positions Sen. Hagel has taken on a range of critical national security issues in recent years, which we will fully consider in the course of his confirmation process before the Senate Armed Services Committee.”

McCain will have the opportunity to pose his questions as the top Republican on that committee.

“I have a clear record of almost always giving the administration the benefit of the doubt, Republican or Democrat,” he said on CBS. “But in this particular case, ‘advise and consent’ is still a role that we play as senators.”